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Subject: search.filters.subject.sound absorption coefficient

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    Impact of Density and Porosity on the Sound Absorption of Binder-Free Aggregated Rice Husk
    (2025-11-01)
    Danworaphong, Sorasak
    ;
    Eadkhong, Thammarong
    This study explores the use of binder-free rice-husk aggregates, a widely available agricultural byproduct, as a sustainable alternative for sound absorption in building applications. We assessed the material’s efficacy by conducting experiments using cylindrical housings that were filled with rice husk aggregate. The aggregates were then tested in an impedance tube according to the ASTM E1050 standards in the frequency range of 400 to 6,000 Hz. The porosity was measured using an air pycnometer. The resulting average sound absorption coefficient (α<inf>avg</inf>) was modeled in terms of the porosity and the density with quadratic equations. Thus, if either property is known, α<inf>avg</inf> can be predicted. The highest recorded value of α<inf>avg</inf> was 0.81. This study underscores the environmental and practical advantages of using binder-free rice husk, especially given its local availability and the absence of binders. The findings also open avenues for sustainable construction materials and could contribute to eco-friendly noise-control applications.
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    Sound Absorption Properties of Natural Fiber Composite from Areca Nut Shells Fibers with Polyvinyl Alcohol
    (2025-01-01)
    Kalasee, Wachara
    ;
    Eakvanich, Visit
    ;
    Rachsiriwatcharabul, Natworapol
    ;
    Wattana, Wassachol
    ;
    Dangwilailux, Panya
    This research investigates the development of sound-absorbing composites using areca nut shells fibers (ANS) bonded with polyvinyl alcohol glue, aiming to create an environmentally friendly and sustainable alternative to conventional synthetic materials. The research explores the effects of varying thicknesses (10, 20, and 30 mm) and fiber lengths (10, 20, and 30 mm) on the sound absorption performance of the composites. The sound absorption coefficient (SAC) was measured using the impedance tube method to determine the composites’ effectiveness across different frequency ranges. The results indicate that the thickness of the composite significantly enhances sound absorption, particularly in the low-frequency range (1,500–2,500 Hz). Composites with a fiber length of 30 mm demonstrated the most effective sound absorption properties at 0.90 above 1,600 Hz (ANS-T30-L30). Additionally, blending fibers of different lengths led to SAC changed behavior. This study contributes to the growing body of knowledge on sustainable materials by utilizing agricultural waste to produce functional and eco-friendly sound-absorbing composites.
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    Sound Absorption of Natural Fiber Composite from Sugarcane Bagasse and Coffee Silver Skin
    (2023-01-01)
    Kalasee, Wachara
    ;
    Lakachaiworakun, Putipong
    ;
    Eakvanich, Visit
    ;
    Dangwilailux, Panya
    This study aimed to develop a sound-absorbing composite using sugarcane bagasse (SB) and coffee silver skin (CS) as raw materials. The composite boards were manufactured by bonding the fibers with Melamine Urea-Formaldehyde adhesive, ensuring a consistent thickness of 30 mm. Various densities were employed, namely 380, 450, and 520 kg/m<sup>3</sup>. The samples were fabricated with different fiber ratios, including SB100%, SB75% with CS25%, and SB50% with CS50%. The sound absorption coefficient (SAC) and noise reduction coefficient (NRC) were measured using the impedance tube method within a frequency range of 63–6,300 Hz. The experimental results revealed that the mixing ratio of CS exerted a notable influence on enhancing the SAC, while the density of the composite board exhibited a significant impact on increasing both the SAC and NRC. Among the densities tested, the optimal value was observed at 520 kg/m<sup>3</sup>, yielding a SAC value of 0.65 at a frequency of 1,000 Hz and an NRC value of 0.55 for the SB50-CS50 composite plate. These findings underscore the importance of considering the CS mixing ratio and composite board density when aiming to optimize sound absorption properties.